Yes a raw stream from a microphone is just buffers of pcm audio which have no information attached to them like length or encoding. So any program you pass it too wouldn’t know what to do with it. Wav data on the other side has riff headers embedded in it which will provide all that information. That’s why when you want to convert or play raw audio in any tool you actually will have to enter that information manually. The question is if sepia is streaming the raw data from the microphone or if it is actually streaming wav chunks that have headers?
I really recommend you read the white paper about the voice2json pipeline by mike the developer:
